A summary of the gender, age, and serum CCL2 levels of the study subjects is shown in Table 1. Individual CCL2 levels are shown in Additional file 1, Table S1. The pairwise comparisons of the groups is shown in Additional file 3, Tables S3 and S4. The mean CCL2 level in the serum of the mesothelioma patients is significantly elevated compared to the Possibly Exposed (no apparent disease) group, and this increase is dependent on the stage of the disease.
Table 1: Gender, age, and serum CCL2 levels of the study subjects.
(Individual patient data is shown in Table S1)
|
Number of
Patients
|
Gender
|
Age
|
Serum CCL2
(pg/ml)
|
Women
|
Men
|
Unexposed
(no apparent disease)
|
41
|
10
|
31
|
56.0 ± 20.0
|
275.2 ± 98.2
|
|
Possibly Exposed
(no apparent disease)
|
356
|
33
|
323
|
68.7 ± 8.3
|
307.5 ± 117.7
|
|
Mesothelioma
(all patients)
|
50
|
5
|
45
|
72.5 ± 8.6
|
421.3 ± 295.1
|
a,b
|
Mesothelioma
(stage 1 patients)
|
12
|
0
|
12
|
72.8 ± 9.1
|
289.9 ± 115.4
|
|
Mesothelioma
(stage 2 patients)
|
5
|
0
|
5
|
75.6 ± 7.1
|
281.0 ± 111.2
|
|
Mesothelioma
(stage 3 patients)
|
14
|
1
|
13
|
74.3 ± 10.7
|
486.0 ± 333.4
|
c,d
|
Mesothelioma
(stage 4 patients)
|
19
|
4
|
15
|
70.2 ± 6.8
|
493.5 ± 346.7
|
c,d
|
a Different from the Unexposed (no apparent disease) group at p < 0.01.
b Different from the Possibly Exposed (no apparent disease) group at p < 0.05.
c Different from the Unexposed (no apparent disease) and the Possibly Exposed (no apparent disease) groups at p < 0.001.
d Different from the Mesothelioma (stage 1 patients) group at p < 0.01.
It is known that serum CCL2 levels increase with age [61-63], and as can be seen in Table 1 the mean CCL2 level in the serum of the Possibly Exposed (no apparent disease) group, age 68.7 ± 8.3 yrs, is higher than that of the Unexposed (no apparent disease) group, age 56.0 ± 20.0 yrs: the age ranges of the study participants are shown in Additional file 2, Table S2. Analysis of the age of the patients using the Kruskal-Wallis (one-way ANOVA) test shows an age difference between the patients in the different groups (p < 0.05). Fisher's exact test also shows a gender difference between groups (p < 0.05): see Methods for the gender of the study participants. Therefore, the data was re-analyzed based on covariates of age (67.97) and gender (1.11). In Tables 2-5, Analysis of Variance (ANOVA) was used to calculate the estimated marginal means and standard error. Subsequently, Analysis of covariance (ANCOVA) was used to compare the estimated marginal means adjusted for covariates of age and gender.
Tables 2 and 3 show the unadjusted serum CCL2 means and 95% confidence intervals and the estimated CCL2 means and 95% confidence intervals when the data is adjusted based on the covariates of age and gender. In Table 2, the data was adjusted using the Unexposed (no apparent disease), Possibly Exposed (no apparent disease), and Mesothelioma (all patients) groups. The pairwise comparisons of these groups is shown in Additional file 3, Table S5. In Table 3, the data was adjusted using the Unexposed (no apparent disease), Possibly Exposed (no apparent disease), and Mesothelioma stages 1-4 groups. The pairwise comparisons of these groups is shown in Additional file 3, Table S6. After adjusting the data, the estimated mean CCL2 level in the serum of the mesothelioma patients is significantly elevated compared to the Possibly Exposed (no apparent disease) group, and this increase is dependent on the stage of the disease.
Table 2: Serum CCL2 levels of the study subjects after adjusting the data for the covariates of gender and age.
|
Unadjusted Data (ANOVA)
|
Adjusted Data (ANCOVA)
|
|
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Estimated
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Lower
Limit
|
Upper
Limit
|
Lower
Limit
|
Upper
Limit
|
Unexposed
(no apparent disease)
|
275.2
|
|
22.9
|
230.2
|
320.3
|
303.5
|
|
24.2
|
256.0
|
351.1
|
Possibly Exposed
(no apparent disease)
|
307.5
|
|
7.8
|
292.2
|
322.8
|
305.6
|
|
7.7
|
290.4
|
320.8
|
Mesothelioma
(all patients)
|
421.3
|
a,c
|
20.8
|
380.5
|
462.1
|
411.8
|
b,c
|
20.8
|
370.9
|
452.6
|
a Different from the Unexposed (no apparent disease) group at p < 0.001
b Different from the Unexposed (no apparent disease) group at p < 0.01
c Different from the Possibly Exposed (no apparent disease) group at p < 0.001
Table 3: Serum CCL2 levels of the study subjects after adjusting the data for the covariates of gender and age.
|
Unadjusted Data (ANOVA)
|
Adjusted Data (ANCOVA)
|
|
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Estimated
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Lower
Limit
|
Upper
Limit
|
Lower
Limit
|
Upper
Limit
|
Unexposed
(no apparent disease)
|
275.2
|
|
22.9
|
230.2
|
320.3
|
305.5
|
|
24.2
|
256.0
|
351.1
|
Possibly Exposed
(no apparent disease)
|
307.5
|
|
7.8
|
292.2
|
322.8
|
305.4
|
|
7.7
|
290.4
|
320.8
|
Mesothelioma
(stage 1 patients)
|
289.9
|
|
41.5
|
208.4
|
371.4
|
275.7
|
|
41.1
|
195.0
|
356.5
|
Mesothelioma
(stage 2 patients)
|
281.0
|
|
64.4
|
154.7
|
407.3
|
261.0
|
|
63.6
|
136.0
|
386.0
|
Mesothelioma
(stage 3 patients)
|
486.0
|
a,c,d
|
38.4
|
410.5
|
561.5
|
471.4
|
b,c,d
|
38.1
|
396.4
|
546.3
|
Mesothelioma
(stage 4 patients)
|
493.5
|
a,c,d
|
33.0
|
428.7
|
558.3
|
492.5
|
a,c,d,e
|
32.7
|
428.3
|
556.7
|
a Different from the Unexposed (no apparent disease) group at p < 0.001
b Different from the Unexposed (no apparent disease) group at p < 0.01
c Different from the Possibly Exposed (no apparent disease) group at p < 0.001
d Different from the Mesothelioma stage 1 patients group at p < 0.01
e Different from the Mesothelioma stage 2 patients group at p < 0.05
Two patients in the Mesothelioma group, patients 31 and 50 (Table S1), had extraordinarily high levels of serum CCL2. Removal of these two patients reduces the serum CCL2 levels in the mesothelioma all patients, stage 3 patients, and stage 4 patients groups to 368.5 ± 138.1, 402.7 ± 123.2, and 420.5 ± 141.9, respectively. Tables 4 and 5 show the results when these two patients are removed from data analysis. Table 4 shows the unadjusted serum CCL2 means and 95% confidence intervals and the estimated CCL2 means and 95% confidence intervals when the data is adjusted based on the covariates of age and gender using the Unexposed (no apparent disease), Possibly Exposed (no apparent disease), and Mesothelioma (all patients) groups. The pairwise comparisons of these groups is shown in Additional file 3, Table S7. Table 5 shows the unadjusted serum CCL2 means and 95% confidence intervals and the estimated CCL2 means and 95% confidence intervals when the data is adjusted based on the covariates of age and gender using the Unexposed (no apparent disease), Possibly Exposed (no apparent disease), and Mesothelioma stages 1-4 groups. The pairwise comparisons of these groups is shown in Additional file 3, Table S8. After removal of patients 31 and 50 from the data analysis, CCL2 levels in the mesothelioma patients are still significantly higher than the CCL2 levels in the Unexposed (no apparent disease) and the Possibly Exposed (no apparent disease) groups, and this increase is dependent on the stage of the disease.
Table 4: Serum CCL2 levels of the study subjects after removing patients 31 and 50 and adjusting the data for the covariates of gender and age.
|
Unadjusted Data (ANOVA)
|
Adjusted Data (ANCOVA)
|
|
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Estimated
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Lower
Limit
|
Upper
Limit
|
Lower
Limit
|
Upper
Limit
|
Unexposed
(no apparent disease)
|
275.2
|
|
18.492
|
238.900
|
311.587
|
308.6
|
|
19.255
|
270.739
|
346.423
|
Possibly Exposed
(no apparent disease)
|
307.5
|
|
6.276
|
295.200
|
319.867
|
305.4
|
|
6.138
|
293.319
|
317.446
|
Mesothelioma
(all patients)
|
368.5
|
a
|
17.091
|
334.911
|
402.089
|
356.0
|
b
|
16.889
|
322.787
|
389.175
|
a Different from the Unexposed (no apparent disease) and the Possibly Exposed (no apparent disease) groups at p < 0.01
b Different from the Possibly Exposed (no apparent disease) groups at p < 0.05.
Table 5: Serum CCL2 levels of the study subjects after removing patients 31 and 50 and adjusting the data for the covariates of gender and age.
|
Unadjusted Data (ANOVA)
|
Adjusted Data (ANCOVA)
|
|
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Estimated
Serum CCL2
(pg/ml)
|
Std
Error
|
95% CI
|
Lower
Limit
|
Upper
Limit
|
Lower
Limit
|
Upper
Limit
|
Unexposed
(no apparent disease)
|
275.2
|
|
18.289
|
239.298
|
311.190
|
305.5
|
|
24.2
|
256.0
|
351.1
|
Possibly Exposed
(no apparent disease)
|
307.5
|
|
6.207
|
295.335
|
319.732
|
305.4
|
|
7.7
|
290.4
|
320.8
|
Mesothelioma
(stage 1 patients)
|
289.9
|
|
33.807
|
223.474
|
356.360
|
275.7
|
|
41.1
|
195.0
|
356.5
|
Mesothelioma
(stage 2 patients)
|
281.0
|
|
52.373
|
178.067
|
383.933
|
261.0
|
|
63.6
|
136.0
|
386.0
|
Mesothelioma
(stage 3 patients)
|
402.7
|
b
|
32.480
|
338.856
|
466.529
|
471.4
|
|
38.1
|
396.4
|
546.3
|
Mesothelioma
(stage 4 patients)
|
420.5
|
a,c,d
|
27.603
|
366.250
|
474.750
|
492.5
|
b,c,d
|
32.7
|
428.3
|
556.7
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
a Different from the Unexposed (no apparent disease) group at p < 0.001
b Different from the Unexposed (no apparent disease) group at p < 0.05
c Different from the Possibly Exposed (no apparent disease) group at p < 0.01
d Different from the Mesothelioma stage 1 patients group at p < 0.05